Method and apparatus for pumping volatile liquids



Nov. 3, 1953 c. J. SCHlLLlNG 2,657,541

METHOD AND APPARATUS FOR PUMPING VOLATILE LIQUIDS Filed April 10, 1950 INVENTOR 92 CLARENCE J. SCHILLING ATTORNEY Patented Nov. 3, 1953 UNITED STATES PATENT OFFICE METHOD AND APPARATUS FOR PUMPING VOLATILE LIQUIDS Clarence J. Schilling, Allentown, Pa., assignor to Air Products Incorporated, a corporation of Michigan Application April 10, 1959, Serial No. 155,021

like normally gaseous product in'the liquid con- 1 dition or any liquid volatile under the pumping conditions.

In the preparation and use of certain liquids having extremely low boiling points at atmospheric pressure, it is ofteii'highly economical and desirable to transfer them from one point to another in the liquid rather than in the gaseous condition. For example, it is now common practice to transport and store liquefied petroleum gases in large quantities in tank of sufficient strength to withstand the vapor pressure of the liquefied gas. Such liquefied gases have, on occasion, to be transferred in liquid phase at a controlled rate from transport to storage tanks or from storage tanks to a vaporizer where they are vaporized for delivery into a distribution system at desired pressure. The use of the present invention is a simple and convenient means for effecting such transfer.

It is also common practice to store oxygen and other so-called permanent gases, in the liquefied form, and to bring them back to the gaseous condition when they are to be used or placed in pressure cylinders ready for final distribution. In such cases, the stored liquefied gas is usually at slightly above atmospheric pressure while the conditions of use or distribution may require that the gasified liquid be at'a very high pressure, often up to or over 2500 pounds per square inch. In such service, it is extremely desirable to apply the finally required pressure to the liquid rather than to the gaseous phase, as both the cost of power and apparatus required in the former case are small fractions of the corresponding figures in the latter.

In pumping liquids which, at normal atmospherie pressure, boil at temperatures ranging from zero degrees centigrade to 190 below centigrade zero, great difliculty is experienced in keeping a pump in operation. At the lower temperaturesflthe heat head between the atmosphere and the liquid stream is so great that even the best of insulation becomes relatively ineifective. In consequence, some atmospheric heat leaks into the liquid on the suction side of the pump and, as the liquid is usually just at its boiling point, any input of heat causes the evolution of gas, which has the 'eifect of reducing the effective stroke length and finally of locking the pump. Even with the h gher boi ng l qu ds n class, wh

11 Claims. (oi. 62-1) pumping against considerable back pressure, the

all

liquid is heated somewhat by the very act of increasing its pressure and any liquid leaking back past the discharge valve, into the pump 1 cylinder, may partially vaporize under intake stroke conditions, resulting in vapor lock.

In all cases the actuating end of the pump, the end to which power. is applied, is almost necessarily in contact with the atmosphere and at a temperature much higher than that of the liquefled gas, the metallic structure of the pump thus transmitting atmospheric heat to the stream being pumped.

Additionally, because of the impossibility of lubricating the plunger packing most effectively, more or less heat 'is produced by rod friction and added to the atmospheric heat tending to raise the temperature of the stream at the suction end of the pump.

One remedy that has been proposed for these difliculties is subcooling the liquid stream to be pumped to a temperature below its boiling point under the conditions existing in the pump cylinder'during the suction stroke so that gas locking of the pump is'avoided.

It has been previously proposed to subcool the liquid stream to be pumped by putting the liquid to bepumped under an increased pressure such that the liquid being pumped will not flash into vapor under the influence of suction. This initial pressure elevation is, in general, a relatively small part or fraction of the total pressure elevation to be attained and has been accomplished in several diflerent ways. One way in which this has been accomplished is to apply an increase in pressure to the supply body of the volatile material by gasifying a small portion of the material and applying the same to the surface of the supply body while in a closed container. A second way in which this initial pressure elevation has been attained is to provide an auxiliary source of pressure which may be temporarily applied to the surface ofthe supply body of volatile material while in a closed container. This is readily achieved in practice by providing a cylinder of gaseous material under a relatively high pressure and supplying the same during the period of transfer to the surface of the volatile material in the storage container. A third manner of accomplishing this result has been to elevate the storage container to a height so that the liquid delivered to the pump is under a static pressure equivalent to the desired degree of subcooling. A fourth method proposed ha been to increase the supplypressure directly by use of a force pump. Thus, the force pump delivers the volatile liquid being pumped to the main pumping step at a pressure sufficiently above the boiling point pressure corresponding to the temperature of the liquid being delivered so that vaporization during the main step is prevented.

An important object of the present invention is the provision of new and improved method and apparatus for pumping highly volatile liquids without vapor locking the pump.

A further important object of the present invention is the provision of a new and improved method and apparatus for pumping highly volatile liquids which tend to vapor lock the pump,

utilizing only the liquid being pumped to prevent such vapor locking.

A further important object of the present invention is the provision of a new and improved method and apparatus for pumping highly vola-' tile liquids which tend to vapor lock the pump, utilizing the pressure of the liquid which has been pumped to prevent such vapor locking.

A further important object of the present invention is the provision of a new and improved method and apparatus for pumping highly volatile liquids which tend to vapor lock the pump, in which refrigeration for preventing such vapor lockin of the pump is obtained by expanding a portion of the liquid to be pumped and in which repressurizing of the expanded portion is brought about and utilized for subcooling the liquid on the way to the pump.

A further important object of the present invention is the provision of a new and improved method and apparatus for pumping highly volatile liquids which tend to vapor lock the pump, in which a portion of the liquid to be pumpedis ex panded for refrigeration purposes and the pressure of the liquid pumped is utilized to repressurize the expanded portion and return the same to the liquid to be pumped.

A further important object of the present invention is to provide a new and improved method and apparatus for pumping highly volatile liquids which tend to vapor lock the pump, utilizing available pressure differentials in an injector for subcooling the liquid on the way to be pumped.

A further important object of the present invention is to provide a new and improved method and apparatus for pumping highly volatile liquids which tend to vapor lock the pump, utilizing available pressure differentials in an injector for returning to the liquid to be pumped expanded fluid from the liquid.

Other objects and the nature and advantages of the instant invention will be apparent from the following description taken in conjunction with the accompanying drawings wherein:

Figure 1 is a diagrammatic view illustrating one form of the invention in which a portion of the liquid to be pumped is expanded, subcools the mainstream, is compressed, reliquefied and utilized as the pressure component for raising the pressure on the main stream to be pumped, and

Figure 2 is a diagrammatic view illustrating a modified form of the invention in which a portion of the pumped fluid is utilized as the pressure component for the injector.

Referring now to the drawings, and particularly to Figure l, is denotes a storage container or reservoir which is well insulated and adapted for holding at its boiling point a supply of the liquid to be pumped. An inlet conduit H is provided controlled by valve 12 for admitting liquid to the container. An outlet con uit 3 s S Q E leading from the bottom of the container to the intake of an injection device l4. Conduit it leads from the discharge side of the injection device [4 to a passageway 15 through heat exchanger H' and conduit l8 conducts the liquid from the passageway It to the intake it or" a re ciprocating pump 20.

A pump for volatile liquids which have boiling point temperatures materially below 273 K. at atmospheric pressure is shown in United States Patent 2,439,957 to Carl R. Anderson. This pump is so designed that the transfer of either atmospheric or frictional heat through the pumping apparatus to the liquid is reduced to the lowest possible amount. This is accomplished by the provision of a cold fluid jacket surrounding the working barrel of the pump, the insulation of the pump cylinder from the metal of the pump frame and other mechanical features. It is proposed to utilize such a pump in conjunction with the pres ent invention. The pump 20 thus includes as the main working parts, a pump cylinder, a plunger ,reciprocated therein, inlet and outlet valves, a. cooling jacket, a connecting rod and any suitable'type of prime mover as indicated at 2|.

A conduit 22 connects the pump discharge 23 with a second heat exchanger 24. The pumped fluidleaves the heat exchanger 24 through conduit '25 which may lead to a suitable vaporizer and thence to-a service line to which may be connected one or more gas receivers, not shown.

Conduit 26 connects with conduit is at diversion point 21 downstream from the injector M for diverting a portion of the liquid flowing to the pump to an expansion valve 28, through conduit 29 and control valve 3!] to a second passageway through the heat exchanger ii in heat exchange relation to passageway Iii. Conduit 31 connects the outlet of the second passageway through the heat exchanger i'i' with the pump cooling jacket 32. At point 33 in conduit 26 downstream from the expansion valve 28, a conduit 34, controlled by valve 35, supplies a by pass around heat exchanger ll connecting with conduit 3| at point 36, thus leading directly from the expansion valve 28 to the pump cooling jacket 32. Conduit 31 is shown as connecting the outlet i'rom the pump cooling jacket 32 with a blower 38 which compresses the gaseous stream flowing through conduit 31. The conduit 39 connects the discharge from blower 35 with a passageway as through the heat exchanger 2 and conduit t! leads from passageway 40 to the nozzle of the injector l4.

In operation, a portion of the liquid to be pumped'is diverted at point 2? through conduit 25 and is expanded in passing through expansion valve 23. The stream is cooled by this expansion, and the cold so produced is used to cool the main stream of liquid to be pumped flowing in con duit [Si by heat exchange therewith in the exchanger H. The expanded stream is then passed through the cooling jacket 32 of the pump 29 to cool the pump. The vapor, or mixture of vapor and liquid, leaving the pump jacket is compressed in the blower (it. The compressed vapor is now reliquefied by heat exchange in exchanger 25 with the main stream of liquid which has been pumped to the desired pressure in the pump 2i]. The reliquefied compressed stream 'iiows through-conduit ii to the-nozzle 320f the injector I l-where it'is utilized as the pressure or velocity component in the injector l4 ior pressurizi-ng-the stream of liquid flowing in the conduit I3 from the source of supply. By means of injector I4, the pressure on the liquid passing to the pump is raised, which has the effect of subcooling the stream to be pumped; hencethe liquid is no longer at its equilibrium temperature at the higher pressure, and the tendency to vaporize during pumping is removed.

After the system is in operation, the subcooling due to the injector will normally be sufficient so that the additional subcooling in the heat exchanger 11 is no longer necessary. In such event, the valve 30 in line 29 may be closed, and the expanded stream may be by-passed around the heat exchanger I 1 directly to the pump cooling jacket 32. The expanded stream is then passed to the blower 38 and reliquefier 24 and is used as the pressure component in the injector 14. In normal operation, the heat exchanger 11 and the pump jacket 32 are maintained with the parts to be cooled submerged in the boiling cooling liquid, the vapors passing off from the boiling liquid going to the blower 38 for com pression and reliquefaction in the reliquefier 24. The level of the boiling liquid is maintained by control of the amount of fluid passing through the expansion valve 28. The diagrammatic showing in the drawings would necessitate manual control, but obviously any suitable automatic control of this valve could be used, a float control being the simplest example. Of course, if desired, no liquid level control need be used and a slight excess of liquid expanded, in which case a mixture of liquid and vapor will go to the blower 38 and liquefier 24. In'the latter, the vapor in the mixture will be condensed. Thus, where the term "vapor is used herein and in the appended claims to refer to the eifiuent of these cooling steps, the presence of some liquid is not ruled out. The important factor is that the expanded liquid cools the stream to be pumped or the pump itself by being at a lower temperature, the amount of cooling being influenced by the availability of the latent heat during vaporization,

In starting up the system, a cylinder containing a gas under pressure may be used as the pressure stream to the injector, thus giving the subcooling effect, and the heat exchanger I1 could be dispensed with entirely. For this purpose, a conduit 43 controlled by valve 44 is shown leading to the nozzle d2 of the injector M from a cylinder (not shown). It may be found desirable to utilize both the sub-cooling due to the injector, and the subcooling due to the heat exchange With the expanded portion of the liquid, in normal operation. If the second subcooling step is found to be unnecessary, it may be discontinued after the injector is in operation, or it may be omitted entirely using a cylinder of compressed gas through conduit 43 to start up the injector. It should be understood the second subcooling step may be of any type and is not limited to the heat exchange with an expanded portion of the stream. Any other suitable means may be employed.

A modified system is shown in Figure 2. Referring to this figure, the numeral 44 designates any conventional two-stage fractionating column, including a high pressure section 45 and a low pressure section 46, each supplied with a stack of bubbling plates. The two sections to the column are separated by a conventional downwardly draining condenser 41, the condensate from which drains into the high pressure section of the column. Compressed air enters the high pressure section of the column at a medial height. In this section of the column, the feed air is fractionated into a substantially pure gaseous nitrogen rising into the condenser 41 and acrude oxygen product collecting in the pool 49 at the base of the column. The crude oxygen product is transferred through conduit 50 and expansion valve 5| to the low pressure section of the column at a medial point therein. The nitrogen rich as rising in the condenser is liquefied, part falling into the pool or reservoir 52 and part falling onto the top plate of the lower section 45 where it acts as reflux for the lower section. Liquefied nitrogen from pool 52 is transferred through conduit 53 and expansion valve 54 to the top of the upper section in which it acts as reflux. The high pressure nitrogen stream and the high pressure oxygen stream flowing into the low pressure section of the column are fractionated in the well-known manner to substantially pure oxygen and a slightly impure nitrogen product. The nitrogen prodnot in gaseous form is withdrawn through conduit 55 at the top of the column. The pure oxygen product formed in the low pressure-section of the column is collected in the pool or reservoir 56 at the lower end thereof and is removed in liquid form through conduit 51. Conduit 51 leads to a passageway 58 through heat exchanger 59. Conduit 68 leads from the passageway 58 to the intake chamber of an injector 6| Ihe injected stream passes from the injector 6| through conduit 62 to the inlet valve 63 of a reciprocating pump 64.

' The pump may be similar to the pump described above in Figure 1, and is driven by a prime mover 65.

A conduit 66 connects the pump discharge valve 61 with a vaporizer 68 wherein the pumped liquid stream is heated and vaporized and then passed through conduit 69 to the service line 16 to which may be connected one or more gas receivers H.

' A conduit 12 connects with conduit 51 at a point 13 between the fractionating column 44 and the heat exchanger 59 for diverting a portion of the stream of liquid flowing to the pump. This divertedportion passes through expansion valve 14, control valve 15 andthence through a second passageway in the heat exchanger 59. Conduit 16 connects the second passageway of the heat exchanger and a cooling jacket 11 surrounding the liquid conveying end of pump 64. At point 18 in conduit 12 downstream from the expansion valve 69, a conduit 19 is shown controlled by valve 89 for by-passing the heat exchanger 59 and connecting with conduit 16 at point 8|, thus leading directly from the expansion valve 14 to the pump cooling jacket 11. Conduit 82 con nects the outlet from the pump cooling jacket with the intake chamber of injector 6|. At point 83 in conduit 66 between the pump discharge and the vaporizer 68, a conduit 84 is shown for diverting a portion of the high pressure liquid flowing from the pump in conduit 66 through conduit 84, valve 85 and conduit 85 to the nozzle 81 of the injector 6!. At point 88 in conduit 69 downstream from the vaporizer 64, a conduit 89 controlled by valve 98 is shown for diverting a portion of the high pressure gas flowing from the vaporizer to the cylinders 1|. This diverted portion can flow to the nozzle81 of the injector 6| through conduit 86. A conduit 9| controlled by valve 92 also leads to the nozzle 81 of the injector 6 I.

In the operation of the form of the invention shown in Figure 2, a portion of the liquid flowing from the fractionating column M through conduit 51 to the pump 64 is diverted through conduit 12 to an expansion valve 14. The stream is expanded in passing through the expansion valve and is thus cooled. The cold so produced is utilized to subcool the main stream of liquid to be pumped flowing in conduit 51 by heat exchange therewith in the exchanger 59. The expanded stream is then passed through the cooling jacket 11 of the pump 64 to cool the pump. The stream leaving the pump jacket through conduit 82 is conducted to the injector 6|. This stream may be entirely gaseous or partly liquid, if more liquid than necessary is expanded, as explained above in connection with Figure 1. The main stream of liquid to be pumped, which has been cooled in the exchanger 59 flows likewise to the injector 6! through conduit 60.

The pressurized stream leaving the injector 6| flows through conduit 62 to the inlet valve 63 of the pump 64 and is pumped to the desired pressure. A portion of the pumped liquid can be diverted through conduits 84 and 86 and utilized as all or part of the pressure stream flowing to the nozzle 81 of the injector Bl. The pressure stream flowing through the nozzle 81 into the injector 6i pressurizes, and thus in effect subcools, the stream of liquid to be pumped flowing through conduit 60 as well as the diverted portion flowing through conduit 82. The pumped stream of liquid leaving the pump through discharge valve 61 and conduit 66 is vaporized by heating in the vaporizer 68 and may be stored as indicated in the cylinders II. The heat for the vaporizer may be supplied in any desirable manner, but preferably by means of a stream of a warm fluid,- such as the air to be separated. A portion of the high pressure gas flowing to the cylinders H may be diverted through conduits 89 and 86 and utilized as all or part of the pressure stream flowing to the nozzle 81 of the injector 6!. Thus, by proper control of the valves 85 and 90, the velocity or pressure component flowing to the injector nozzle may be either a portion of the liquid under pressure flowing from the pump, a portion of the compressed gas leaving the vaporizer, or a combination of both.

Once the injector is in normal operation, sufflcient subcooling will be obtained by the injection of the pressure stream into the stream to be pumped so that additional subcooling in the heat exchanger 59 may become unnecessary. In such event, the valve 15 is closed so that the expanded stream flows directly from the expansion valve Hi to the pump cooling jacket 11, and thence to the injector 6| through conduit 82, where the expanded stream is pressurized and returned to the stream to be pumped by the portion of the pumped fluid passing to the nozzle 81 of the injector.

If other means are provided for cooling the pump, both valves 15 and 80 can be closed and the stream of liquid to be pumped would then flow directly from the storage container through the idle heat exchanger 59 to the injector 6|. It should be noted that the additional subcooling step is not limited to the form shown, but that any other suitable means for subcooling could be utilized.

In starting up ing a gas under pressure is attachedto the conthe system, a cylinder containduit 9| and is fed directly to the injector nozzle 81, where it is used as the pressure stream to the injector until such time as the pumped fluid is under suflicient pressure to be used as the injecting means. In operating in this manner. the heat exchanger 59 may be dispensed with entirely.

Thesystem shown in Figure 2 is quite flexible and is adaptable to pumping various fluids from the column under varying conditions. It is possible to obtain a subcooling effect by use of the injector alone, or if desirable the subcooling may be obtained by both the injector and by the heat exchange with an expanded portion of the stream to be pumped.

Iclaim:

1. The method of pumping a highly volatile liquid from a reservoir in which the liquid is maintained at a pressure corresponding to its equilibrium boiling point temperature by a pump having a liquid conveying end to a receiving means at a relatively high pressure comprising forming a stream of the liquid under the pres- .sure maintained in the reservoir forming an auxiliary stream of liquid, expanding the auxiliary stream of liquid to a lower pressure to form a stream of fluid colder than the stream of liquid from the reservoir, heat exchanging the colder stream against the liquid conveying end of the pump to prevent vaporization of liquid being pumped and thereby forming an effiuent colder stream, subcooling the stream of liquid from said reservoir, passing the subcoole'd stream to the pump and raising the pressure of the eflluent colder stream from the heat exchange step and introducing the effluent stream into the stream of liquid from the reservoir.

2. The method of pumping a highly volatile liquid from a reservoir in which the liquid is maintained at a pressure corresponding to its equilibrium boiling point temperature by a pump having a liquid conveying end to a receiving means at a relatively high pressure comprising forming a stream of the liquid under the pres- I sure maintained in the reservoir, forming an auxiliary stream of liquid, expanding the auxiliary stream of liquid to a lower pressure to form a stream of fluid colder than the stream of liquid from the reservoir, heat exchanging the colder stream against the liquid conveying end of the pump to prevent vaporization of liquid being pumped and thereby forming an eiiluent colder stream, forming a stream of fluid from the pumped liquid, passing the effiuentcolder stream from the heat exchange step and the stream of liquid from the reservoir to an injector, and utilizing a stream of fluid from the pumped liquid as the propellent in the injector to raise the pressure of the mixture above the pressure in the reservoir, thus subcooling the stream of mixture and passing the subcooled stream to the pump.

3. Apparatus for pumping a volatile liquid from a reservoir in which the liquid is maintained at a pressure corresponding to its equilibrium boiling point temperature to a receiving means at a relatively high pressure comprismg a pump having an intake and outlet for pumping th liquid to the desired pressure, an injector having an intake chamber, a pressurizing nozzle and a discharge side, a first conduit connected to the intake chamber of the injector for supplying liquid from the reservoir to the injector, a second conduit connecting the discharge side of the injector and the inlet of the pump, a

ae is/i third conduit connected to the-pressurizing nozzle of thei'niector for conducting a stream of fluid under a relatively high pressure to the injector, pump cooling means in heat exchange relation with the liquid conveyingend of the pump, the cooling means having an inlet and an outlet, a fourth conduit connected to the inlet of the pump cooling means forsupplying a cooling fluid thereto, a compressor connected to the outlet of the pump cooling means for compressing fluid therefrom and a connection between the discharge side of the compressor and the third conduit to supply the compressed fluid to th nozzle of the injector. 4;. Apparatus for pumping a volatile liquid from a reservoir in which the liquid is maintained at a pressure corresponding to its equilibrium boiling point temperature to a receiving means at a relatively high pressure comprising a pump having angintake and outlet for pumping the liquid to the desired pressure, an injector having an intake chamber, a pressurizing nozzle and a discharge side, afirstconduit connected to the intake chamber of the injector for supplying liquid from the reservoir to the injector, a second conduit connecting the discharge side of the injector and the inlet of the pump, a third conduit; connected to the pressurizing nozzle of the injector for conducting a stream of fluid under a relatively high pressure to the injector, pump cooling means in heat exchange relation with the liquid conveying end of the pump, the cooling means having an inlet and an outlet, a fourth conduit connected to the inlet of the pump'cooling means for supplying a cooling fluid thereto, a compressor connected to th outlet of the pump cooling means for compressing fluid therefrom, a connection between the discharge side of the compressor and the third conduit to supply the compressed fluid to the nozzle of the injector and fluid expansion means in the fourth conduit for expanding fluid therein to supply the cooling fluid.

5. Apparatus for pumping a volatile liquid from a reservoir in which the liquid is maintained at a pressure corresponding to its equilibrium boiling point temperature to a receiving means at a relatively high pressure comprising a pump having an intake and outlet for pumping the liquid to the desired pressure, an injector having an intake chamber, a pressurizing nozzle and a discharge side, a first conduit connected to the intake chamber of the injector for supplying liquid from th reservoir to the injector, a second conduit connecting the discharge side of the injector and the inlet of the pump, a third conduit connected to the pressurizing nozzle of the injector for conducting a stream of fluid under a relatively high pressure to the injector, pump cooling means in heat exchange relation with the liquid conveying end of the pump, the cooling means having an inlet and an outlet, a fourth conduit connected to the inlet of the pump cooling means for supplying a cooling fluid thereto and a fifth conduit connected between the outlet of the pump cooling means and the intake chamber of the injector.

6. Apparatus for pumping a volatile liquid from a reservoir in which the liquid is maintained at a pressure corresponding to its equilibrium boiling point temperature to a receiving means at a relatively high pressure comprising a pump having an intake and outlet for pumping the liquid to the desired pressure, an injector having an intake chamber, a pressurizing nozzle and a discharge side, a first conduit connected to the .10. intake chamber of the injector for supplying liquid from the reservoir to the injector, a sec.- ond conduit connecting the discharge side of the injector and the inlet of the pump, a third conduit connected to the pressurizing nozzle of the injector for conducting a stream of fluid under a relatively high pressure to the injector, pump cooling means in heat exchange relation with the liquid conveying end of the pump, the cooling means having an inlet and an outlet, a fourth conduit connected to the inlet of the pump cooling means for supplying a cooling fluid thereto, fluid expansion means in the fourth conduit for expanding fluid therein to supply the cooling fluid and a fifth conduit connected between the outlet of the pump cooling means and the intake chamber of the injector.

7. Apparatus for pumping a volatile liquid from a reservoir in which the liquid is maintained at a pressure corresponding to its equilibrium boiling point temperature to a receiving means at a relatively high pressure comprising a pump having an intake and outlet for pumping the liquid to the desired pressure, an injector having an intake chamber, a pressurizing nozzle and a discharge side, a first conduit connected to the intake chamber of the injector for supplying liquid from the reservoir to the injector, a second conduit connecting the discharge side of the injector and the inlet of the pump, a third conduit connected to the pressurizing nozzle of the injector for conducting a stream of fluid under a relatively high pressure to the injector, pump cooling means in heat exchange relation with the liquid conveying end of the pump, the cooling means having an inlet and an outlet, a fourth conduit connected to the inlet of the pump cooling means for supplying a cooling fluid thereto, fluid expansion means in the fourth conduit for expanding fluid therein to supply the cooling fluid, a connection between the outlet of the pump and the third conduit for supplying the pumped liquid to the injector as the pressurizing fluid and a fifth conduit connected between the outlet of the pump cooling means and the intake chamber of the injector.

8. The method of pumping a highly volatile liquid from a reservoir in which liquid is maintained at a pressure corresponding to its equilibrium boiling point temperature by means of a pump having a liquid conveying end to a receiving means at a relatively high pressure comprising, forming a stream of the liquid under the pressure maintained in the reservoir, forming a stream of fluid colder than the stream of liquid from the reservoir, heat exchanging the stream of fluid against the liquid conveying end of the pump thereby forming an efiiuent colder stream, subcooling the stream of liquid from the reservoir, passing the subcooled stream of liquid to the pump, and introducing the effluent stream into the stream of liquid from the reservoir.

9. The method of pumping a highly volatile liquid from a reservoir in which liquid is maintained at a pressure corresponding to its equilibrium boiling point temperature by means of a pump having a liquid conveying end to a receiving means at a relatively high pressure comprising, forming a stream of the liquid under the pressure maintained in the reservoir, forming an auxiliary stream of liquid, expanding the auxiliary stream of liquid to a lower pressure to form a stream of fluid colder than the stream of liquid from the reservoir, heat exchanging the stream of fluid against the liquid conveying end imam or the pump thereby forming an emuent comer stream, 'subcooling the stream of liquid from the reservoir, passing the subcooled stream of liquid to the pump, and introducing the efiiuent stream into. the stream of liquid from the reservoir.

10, Apparatus for pumping a volatile liquid tron; a reservoir in which the liquid is maintained at a pressure corresponding to its equilibrium boiling point temperature to a receiving means at a relatively high pressure comprising, a pump having an intake and an outlet for pumping the liquid to the desired pressure, pressure producing m ans having input means and output m an a first conduit connecting the reservoir and the input means of the pressure producing means for supplying a stream of liquid from the reservoir to the pressure producing means, a second -conduit connecting the output means of the pressure producing means to the intake of the pump, pum cooling means in heat exchange relation with the intake and outlet of the pump, the coolin means having an inlet and an outlet, 9, third conduit connected to the inlet of the pumpcooling means for supplying a cooling fluid thereto andthereby forming an efliuent colder stream at the outlet of the pump cooling means, and a fourth conduit connected to the outlet of the pump cooling means for introducing the emueht colder stream into the stream of liquid from the reservoir.

} 11. Apparatus for pumping a volatile liquid I-roi'n a reservoir in which the liquid is maintained ata pressure corresponding to its equilibrium 1'2 bo ling] point temperature to a receiving means at a relatively high pressure comprising, a pump having an intake and an outlet for pumping the liquid to the desired pressure, an injector having input means and output means, a first conduit connecting the reservoir and the input means of the injebtor for supplying 'a stream of liquid from the reservoir to the injector, a second conduit connecting the output means of the injector to the intake "of the pump, pump cooling means in heat exchange relation with the in take and outlet of the pump, the cooling means haviiig an inlet and an outlet, a third conduit 'c'nnect'ed to the inlet of the pump cooling 'means for supplying a cooling fluid thereto and thereby forming an eifiue'nt colder stream at the outlet or the pump cooling means, and a fourth conduit connected to the outlet of the pump cooling means and the input means of the injecto1 CLARENCE J. SCHILLING.

References Cited in the file oi this patent U'NrrED' STATES PATENTS 

